An official website of the United States government
The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before
sharing sensitive information, make sure you’re on a federal
government site.
The site is secure.
The https:// ensures that you are connecting to the
official website and that any information you provide is encrypted
and transmitted securely.
Xu X, Luo D, Guo C, Rong Q.Xu X, et al.Med Eng Phys. 2017 Aug;46:1-11. doi: 10.1016/j.medengphy.2017.04.012. Epub 2017 Jun 17.Med Eng Phys. 2017.PMID: 28629601
Li Y, Tang K, Xu XL, Yi B.Li Y, et al.Beijing Da Xue Xue Bao Yi Xue Ban. 2012 Feb 18;44(1):75-9.Beijing Da Xue Xue Bao Yi Xue Ban. 2012.PMID: 22353905Free article.Chinese.